Speaker
Description
Rare–earths (Tb3+ or Ce3+) doped zinc aluminate (ZnAl2O4) nanocrystals were successfully prepared by a modified combustion method using urea (CH4N2O, 99–99.5%) as fuel and characterized to investigate down-converted emission by energy transfer from Ce3+ to Tb3+ . The post-preparation annealing of the samples was carried out in a reducing atmosphere of 4%H2/96%N2 mixture at an elevated temperature of 7000C for 4 hours. This was meant to reduce non-emitting Ce4+ to Ce3+ and also to improve crystallinity. As confirmed by X-ray diffraction (XRD) data, the materials were highly crystalline and the XRD patterns were consistent with the closed-packed face centered cubic spinel structure of ZnAl2O4. The photoluminescence excitation and photoluminescence data collected when ZnAl2O4:Ce3+,Tb3+ samples, with different concentrations of Ce3+ and Tb3+ ions, were excited at different wavelengths (230―325nm) showed that green emission of Tb3+ was sensitized by Ce3+, i.e. there was energy transfer from Ce3+ to Tb3+ resulting in improvement of green emission due to the 5D4 → 7F5 transitions of Tb3+ ions. This study therefore, sets out to discuss the sensitizing effect of Ce3+ and the effect of post annealing on the structure of ZnAl2O4:Ce3+,Tb3+. The results indicate the potential of the phosphor powders for applications in luminescent display panels and further development as UV down-converters for improved performance of conventional photovoltaic cells.
| Level (Hons, MSc, <br> PhD, other)? | PhD |
|---|---|
| Consider for a student <br> award (Yes / No)? | Yes |
| Would you like to <br> submit a short paper <br> for the Conference <br> Proceedings (Yes / No)? | Yes |
